1. Field of the Invention
The present invention relates to an elastic support module and a rack bar supporting device for supporting a rack bar for a vehicle steering apparatus, which includes the elastic support module. More particularly, the present invention relates to an elastic support module which can prevent a noise from being produced in a rack bar supporting device for a rack-and-pinion type steering apparatus for a vehicle due to the increase of a clearance caused when the vehicle has lost the driving durability thereof to a certain degree and hence a support yoke of the vehicle is worn, or due to an impact reversely input from a road surface, and hence can provide a pleasant steering feeling for a driver when steering the vehicle. The present invention also relates to a rack bar supporting device for a vehicle steering apparatus, which includes such an elastic support module.
2. Description of the Prior Art
As generally known in the art, a steering apparatus of a vehicle means an apparatus that allows a driver to change a driving direction of the vehicle by his/her will. The steering apparatus helps the driver to optionally change the center of rotation, about which the vehicle's front wheels are turned, so as to make the vehicle move in a direction desired by the driver.
FIG. 1 schematically illustrates a conventional rack-and-pinion type steering apparatus, and FIG. 2 is a cross-sectional view of a conventional rack bar supporting device.
As illustrated in the drawings, a conventional rack-and-pinion type steering apparatus includes: a steering wheel 100 arranged at a driver's seat side; a steering shaft 105 connected to the steering wheel 100; a steering column 103 configured to allow the steering shaft 100 to be fixed to a vehicle body; a gear box 130 provided with a rack gear 110 and a pinion gear 120 to convert a turning force input from the steering shaft 105 to a rectilinear movement; a rack bar 140 provided with an inner ball joint 135 at each end thereof; and a tie rod 150 integrally formed with a ball of the inner ball joint 135.
The tie rod 150 is connected with an outer ball joint 155 and transfers a force to a knuckle 159 to steer a tire 158.
In addition, the conventional rack bar supporting device includes a pinion gear 120, a rack bar 140, a support yoke 260, a spring 263, and a yoke plug 265. As described above, the rack-and-pinion type gear box 130 is adapted to convert a turning force input from a steering shaft (not shown) to a rectilinear movement.
The rack bar 140 is engaged with the pinion gear 120 to convert a turning movement into a rectilinear movement, in which a device for supporting the rack bar 140 in relation to the pinion gear 120 side is provided behind the rack bar 140 so as to facilitate the engagement between the rack bar 140 and the pinion gear 120.
The device for supporting the rack bar 140 includes a support yoke 260, a spring 263, and a yoke plug 265, in which the support yoke 260 is positioned opposite to the rear side of the rack bar 140, on which the rack gear 110 is formed, and is inserted into a cylinder 250 of the gear box 130 to be movable forward and backward perpendicularly to the rack bar 140.
The support yoke 260 is formed in a cylindrical shape so that it can be slid forward and backward, and on the front side thereof where the support yoke 260 is in contact with the rack bar 140, the support yoke 260 is formed with a groove of a semicircular cross-section, so that the front side of the support yoke 260 can be in close contact with the rear side of the rack bar 140.
In addition, in order to assure that the rack bar 140 and the pinion gear 120 can be in close contact with each other and a force can be efficiently transferred therebetween, the spring 263 is arranged behind the support yoke 260 to push the support yoke 260 with a predetermined pressure and a clearance produced between the rack bar 140 and the pinion gear 120 can be compensated.
The support yoke 260 is caused to be frictionally slid against the rear side of the rack bar 140. In order to prevent the rack bar 140 from being worn or producing a noise due to friction, the support yoke 260 is typically formed of a plastic material softer than the rack bar 140.
The spring 263 received in the spring groove 220 serves to apply pressure so that the support yoke 260 comes into close contact with the rack bar 140. Typically, a coil spring is employed as the spring 263, and the yoke plug 265 is positioned behind the spring 263 to support the spring 263.
The yoke plug 265 supports the spring 263, so that the spring 263 can apply pressure to the support yoke 260. Since the yoke plug 265 is typically formed with peaks and valleys of threads so that the yoke plug 265 can be fixedly engaged with the gear box 130 and a lock nut 240, which are formed with peaks and valleys of threads corresponding to those of the yoke plug 265.
However, such a conventional rack bar supporting device has problems in that when the support yoke has lost durability to a certain degree, a clearance between the support yoke and the rack bar is increased to such an extent that the support yoke cannot properly support the rack bar, and due to the increase of the clearance, a rattle noise may be produced from the support yoke and the yoke plug.